$$\left|\sqrt{40\sqrt{2}-57}\right|-\left|\sqrt{40\sqrt{2}+57}\right|$$
Так как $$40\sqrt{2} = \sqrt{1600 \cdot 2} = \sqrt{3200}$$
$$57 = \sqrt{57^2} = \sqrt{3249}$$.
Тогда $$40\sqrt{2} - 57 < 0$$, a $$40\sqrt{2} + 57 > 0$$
$$\left|\sqrt{40\sqrt{2}-57}\right|-\left|\sqrt{40\sqrt{2}+57}\right| = -\sqrt{40\sqrt{2}-57} - \sqrt{40\sqrt{2}+57}$$
Ответ: $$-\sqrt{40\sqrt{2}-57} - \sqrt{40\sqrt{2}+57}$$